Idiopathic restless legs syndrome (RLS) frequently follows an autosomal dominant inheritance with a variable clinical expressivity of symptoms. We describe the largest German kindred of familial RLS with 20 affected and investigated members in four generations with a variety of clinical symptoms. Patients were examined clinically, and polysomnography was performed in selected cases. The diagnosis was set according to the diagnostic criteria of the International RLS Study Group. All patients showed sensory symptoms of their legs and a worsening of symptoms with increasing age. Older patients, who needed treatment, responded well to opioids. Segregation ratios were close to 0.5, confirming a virtually complete penetrance. The mean age of onset fell from 51.5 years in the second generation to 19.8 years in the fourth generation (ANOVA, p = 0.025). The identification of presymptomatic carriers in the fourth generation in the following years, however, may prejudice this result. This large family showed the variety of clinical RLS symptoms with decreasing age of onset in generations II-IV, suggesting at least the possibility of anticipation.